The invention is directed to a covering device for an internal combustion engine having cylinders arranged in a V-shaped manner.
FIG. 1 shows a conventional fuel injection system. As shown in FIG. 1 (exemplifying a six-cylinder engine), a microcomputer 100 calculates a basic fuel injection amount based on intake air pressure information from an intake air pressure sensor (indicating an intake air amount) and rotational speed information from an engine rotational speed sensor, and subjects the basic fuel injection amount to various kinds of modifications based on information from a throttle opening sensor, an engine temperature sensor, and an intake air temperature sensor to calculate a final fuel injection amount corresponding to the operating condition and to calculate fuel injection timing.
Subsequently, output timers 200 to 250 output signals having a period corresponding to the calculated final fuel injection amount to solenoid drivers 300 to 350 at the injection timing calculated by the microcomputer 100, respectively. The solenoid drivers 300 to 350 control the opening and closing of built-in solenoid valves of electromagnetic solenoid type fuel injection valves (that is, injectors) 400 to 450, thereby enabling the fuel to be injected and supplied to the engine.
Combustion chamber direct injection type gasoline engines have been designed and are constructed so as to directly inject and supply fuel into the combustion chamber. Such engines usually realize combustion in the form of a homogeneous air-fuel mixture (wherein the fuel is equally dispersed throughout the entire combustion chamber), and a stratified air-fuel mixture (having (1) a layer of a combustible air-fuel mixture that is ignitable by an ignition plug, and (2) an air layer including recirculated exhaust gas and/or a layer of an air-fuel mixture having a combustible mixture ratio which is difficult to ignite by the ignition plug but is combustible by receiving the combustion flame of the aforementioned layer (1)), in the combustion chamber depending on operating conditions (speed, load condition, and the like). This permits combustion of a super-lean air-fuel ratio (an air-fuel ratio in the vicinity of the lean burning limit), which results in improvement in fuel consumption and the like, due to pumping loss reduction and other factors. Such systems are described, for example, in Japanese Patent Provisional Publication (Kokai) No. 62-191622, Japanese Patent Provisional Publication (Kokai) No. 2-169834, and Press Information entitled "Nissan Direct-Injection Engine" (Document E1-2200-9709 of Nissan Motor Co., Ltd. of Tokyo, Japan). The entire contents of these documents are incorporated herein by reference.
A direct injection type gasoline engine directly injects and supplies fuel into the combustion chamber at a relatively high pressure. This requires a fuel injection pressure higher than the pressure in the combustion chamber and requires a fuel injection pressure higher than that of a conventional intake port-fuel injection type engine.
The use of high pressure injection requires closely controlled opening and closing of the built-in solenoid valves of the fuel injection valves 400 to 450 during predetermined periods at predetermined timings. A slight difference in the opening and closing periods may cause the fuel supply amount to vary widely because the injection pressure is high. Therefore, the solenoid drivers 300 to 350 should be disposed close to the fuel injection valves 400 to 450 as much as possible in order to have signals be unaffected by harness resistance, noise, and the like. The operating voltage of the solenoid valves can be increased in order to provide high pressure injection. This also requires minimization of the voltage drop due to the harness.
However, as shown in FIG. 2, a conventional direct injection type gasoline engine has solenoid drivers at the rear portion of the engine compartment, as is the case with a conventional intake port-fuel injection type engine. Such a design lengthens the harness connecting the solenoid drivers with the fuel injection valves. This causes the signals to the solenoids in the valves to be affected by the harness resistance and noise, and the like, and makes it more difficult to supply fuel in a stable fashion and increases the voltage drop.
In the case of a V-type engine, intake system parts (intake pipe, intake collector, intake manifold, and the like) are disposed above an intermediate space between left and right cylinder banks. The cylinder row that is positioned on the right as viewed facing the front of the engine (the end of the engine to which a transmission is not connected) is referred to as "the right bank", and the left-hand cylinder row is referred to as "the left bank" as shown in FIG. 3. The fuel injection valves, fuel injection piping, and the like are disposed in this intermediate space between the left and right banks.
In a direct injection type gasoline engine, high pressure injection requires raising the fuel pressure (combustion pressure) supplied from the fuel tank to the fuel injection valves. To accomplish this, a high pressure fuel pump may be disposed in a region 500 (a space between the left and right banks at the rear end portion of the engine), as shown in FIG. 4, to be directly driven by a cam.
However, a timing chain cover is disposed at the front end of a conventional V-type engine as shown, for example, in FIG. 4. For noise reduction, to prevent jamming by foreign matter, for safely, and other reasons, conventional timing chain covers 10A, 10B are adapted to surround a crank sprocket 3 attached to one end of a crankshaft 2. Crankshaft 2 receives the reciprocating movement of a piston (not shown) as a torque by rotatably holding one end of a connecting rod (not shown) connected to the piston by a crankpin (not shown). Cam sprockets 6A, 6B, 7A, 7B are attached to end portions of camshafts 4A, 4B, 5A, 5B for actuating intake valves and exhaust valves. A mechanical power transmitting medium (such as a timing chain, various kinds of sprockets, a chain tensioner, and the like) connect the crank sprocket 3 and the cam sprockets 6A, 6B, 7A, 7B to transmit the torque of the crankshaft 2 to the camshafts 4A, 4B, 5A, 5B, and the like. Both the timing chain cover 10A and the timing chain cover 10B sandwich the crank sprocket 3, the cam sprockets 6A, 6B, 7A, 7B, and the power transmitting mechanism 8, and the like therebetween to surround them.
After completion of engine assembly (or in a state where the engine is mounted on the vehicle) when fuel is injected at high pressure, a check is performed for leakage of gasoline from respective fuel injection valves, fuel piping, and connector portions thereof. For example, a fuel leakage checker 700 having a sensor portion 710 for detecting the concentration of HC (hydrocarbons) at a leading end of a bar-like member, as shown in FIG. 5, may be used to check for leakage. The fuel leakage is checked by inserting the sensor portion 710 into a gap between various kinds of parts and bringing it near respective fuel injection valves, fuel piping, and the connector portions thereof.
However, as described above, intake system parts (such as the intake collector and the intake manifold) and the like are disposed just above the fuel injection valves, the fuel piping, and the like. The high pressure fuel pump covers the intermediate space between the left and right banks at the rear end of the engine. The timing chain cover covers the intermediate space between the left and right banks at the front end of the engine. Due to these arrangements, the sensor portion 710 of the fuel leakage checker 700 cannot get near the fuel injection valves, the fuel piping, and the like. This makes it difficult to check for leakage.